The present invention relates to a derivatization apparatus for coating a sample carrier with a reagent solution and to a derivatization method for coating a sample carrier with a reagent solution.
In the field of thin-layer chromatography, the derivatization of samples to be analyzed is frequently carried out by immersing the sample carrier in a solution with reagents or coating the sample carrier with the solution which then penetrates the sample carrier and/or the sample depending on the desired application.
The spraying is known to have the great advantage over the immersion that the measuring areas are less blurry or not blurry at all. A further advantage is the reduced need for reagents required as solvents.
In order to achieve the best results or for the subsequent chemical reaction to run successfully, it is desirable that the reagent solution be applied as homogeneously as possible on the entire sample carrier in an optimum dosage and thickness. If a spraying method is used, this depends on the type of spray head used and on the distance and the exact position of the spray head with respect to the sample carrier. In order to achieve a more uniform distribution, the spray head may also be moved above the sample carrier in such a way that all areas are sprayed evenly.
A typical spray method produces small liquid droplets which are sprayed onto the sample carrier. A certain area may be sprayed more or less evenly depending on the shape of the spray head. This produces a liquid film on the surface of the sample carrier which triggers the desired reaction.
In addition to the direct spraying of the sample carrier, it is also possible to form a mist of fine droplets by means of a spray nozzle, which then settles onto the sample carrier.
WO 2006/114249 discloses such a method and a corresponding apparatus, whereby the homogeneous distribution as well as the need for reagents are optimized by nebulizing the reagent solution. The liquid droplets are produced by ultrasonic atomization. This creates a mist above the liquid in the container, which then settles and deposits the desired liquid film on the sample carrier.
The size of the droplets generated by an ultrasonic atomizer depends on the vibration frequency. The size of the generated drops may vary by up to 25% depending on the frequency selected. This leads to a relatively inhomogeneous mist, and thus to an inhomogeneous liquid film on the sample carrier.
To somewhat obviate this problem, a droplet separator is used in the above-described method in order to prevent too large drops or splashes generated by the spray nozzle from reaching the sample carrier. However, in order to achieve a complete covering of the sample carrier with a liquid film of the reagent solution, an excess of reagent liquid is necessarily present either in the lower part of the liquid container or caught onto the droplet separator before the liquid drops back down into the liquid container next to the sample carrier.
The referenced patent document also shows a gas inlet and/or outlet used to swirl the generated mist in the container in order to achieve a better intermixing and eliminate inhomogeneities in the distribution of the mist.